>Number:         406
>Category:       kern
>Synopsis:       nullfs cannot be unmounted in certain cases
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    gnats-admin (Kernel Bug People)
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Tue Aug  9 17:05:05 1994
>Originator:     Dave Cornejo
>Organization:
Dave Cornejo                                There is nothing so subtle
Dogwood Media                                           as the obvious
Fremont, California
>Release:        
>Environment:
	
System: NetBSD white.dogwood.com 1.0_BETA NetBSD 1.0_BETA (DOGWOOD) #0: Thu Aug 4 07:39:31 PDT 1994 dave@white.dogwood.com:/u1/src/sys/arch/i386/compile/DOGWOOD i386


>Description:
I have found some cases where you apparently cannot unmount a nullfs.
I have a CD-ROM (cd0a) mounted on /cdrom, then from ~ftp/pub I mounted
a nullfs on /cdrom/xxx using the command

  mount -t cd9660 -r /cdrom/xxx xxx

This now cannot be dismounted by using umount on either /cdrom/xxx,
xxx, ~ftp/pub/xxx, or ./xxx.  If you specify the *full path* when you
mount, you can then unmount it using the full path, so

  mount -t cd9660 -r /cdrom/xxx /home/ftp/pub/xxx
  umount /home/ftp/pub/xxx

will work.  I also note that while you can unmount, say sd0h using
either the device or the mount point, you can only use the mount point
with a null fs, which may be appropriate.

It sort of looks like umount wants to see a full pathname for the
mount point.  Either umount or mount should be fixed so that you can't
get into this deadlock.

>How-To-Repeat:
	
>Fix:
	
>Audit-Trail:
>Unformatted:


------------------------------------------------------------------------------